Solutions to Increase PV Hosting Capacity and Provision of Services from Flexible Energy Resources

Abstract

Future smart grids will be more dynamic with many variabilities related to generation, inertia, and topology changes. Therefore, more flexibility in form of several active and reactive power related technical services from different distributed energy resources (DER) will be needed for local (distribution network) and whole system (transmission network) needs. However, traditional distribution network operation and control principles are limiting the Photovoltaic (PV) hosting capacity of LV networks and the DER capability to provide system-wide technical services in certain situations. New active and adaptive control principles are needed in order to overcome these limitations. This paper studies and proposes solutions for adaptive settings and management schemes to increase PV hosting capacity and improve provision of frequency support related services by flexible energy resources. The studies show that unwanted interactions between different DER units and their control functions can be avoided with the proposed adaptive control methods. Simultaneously, also better distribution network PV hosting capacity and flexibility services provision from DER units even during very low load situations can be achieved.

Flexibility Services Provision by Frequency-Dependent Control of On-Load Tap-Changer and Distributed Energy Resources

“…In the previous studies [2]- [4], in order to increase DER hosting capacity and avoid curtailment of PV active power P, QU-droop has been used as a primary voltage control method, and P curtailment by PU-droop control as a secondary method. In [4], the PV hosting capacity with and without BESS at the same LV network connection point was studied with different DER unit droop settings and HV/MV substation transformer OLTC values.…”

“…In the previous studies [2]- [4], in order to increase DER hosting capacity and avoid curtailment of PV active power P, QU-droop has been used as a primary voltage control method, and P curtailment by PU-droop control as a secondary method. In [4], the PV hosting capacity with and without BESS at the same LV network connection point was studied with different DER unit droop settings and HV/MV substation transformer OLTC values. Based on the studies, it was concluded in [4] that flexible weekly/monthly/seasonal and coordinated QU-, PU-and Pf-droop settings (with dead-zones) are needed on LV network-connected PVs and BESSs in order to improve their flexibility services provision.…”

“…In [4], the PV hosting capacity with and without BESS at the same LV network connection point was studied with different DER unit droop settings and HV/MV substation transformer OLTC values. Based on the studies, it was concluded in [4] that flexible weekly/monthly/seasonal and coordinated QU-, PU-and Pf-droop settings (with dead-zones) are needed on LV network-connected PVs and BESSs in order to improve their flexibility services provision. These settings must be coordinated with OLTC settings (see Section II.B).…”

“…These settings must be coordinated with OLTC settings (see Section II.B). It was also stated in [4] that during larger frequency deviations frequency-adaptive PU-droops could enable larger power system frequency support from PV and BESS (when connected to the same point in the LV network) as well as maximise LV network connected demand participation to frequency control. Further, in [4] new real-time adaptive management schemes for PU-droops as well as OLTC setting-dependent QU-droops were proposed in order to further improve the provision of flexibility services.…”

“…For example, different DER units' active (P) and reactive power (Q) control modes, settings and coordination with OLTC settings and other ANM functionalities should be considered already in the planning stage. [1]- [4] Table I presents the proposed and used frequency levels/ranges for market or grid code-based frequency control services in this paper. Different frequency controlrelated marketplaces typically cover frequency levels 1-3 and different grid code requirements will typically consider frequency level 4.…”